Field of the Invention
The present invention relates to an X-ray image capturing device.
Description of Background Art
Conventionally, an X-ray image capturing device is known in which an X-ray transmitted through a subject is detected to image an inside of the subject. Such an X-ray image capturing device is disclosed in, for example, Japanese Unexamined Patent Application Publication No. 2009-254570.
The aforementioned Japanese Unexamined Patent Application Publication No. 2009-254570 discloses an X-ray image capturing device. The X-ray image capturing device is equipped with a top board for laying a subject thereon, an X-ray tube for irradiating the subject with an X-ray, an X-ray detector for detecting the transmitted X-ray from the subject, a support unit for supporting the X-ray tube and the X-ray detector so that the X-ray tube and the X-ray face with each other across the top board, a moving mechanism for relatively moving the support unit and the top board, an image capturing unit for capturing an X-ray transparent image by detecting the transmitted X-ray with the X-ray detector, and an X-ray transparent image output unit for outputting the X-ray transparent image.
The X-ray image capturing device disclosed by the Japanese Unexamined Patent Application Publication No. 2009-254570 is configured as follows. The moving mechanism is controlled so as to relatively move the support unit and the top board so that the X-ray tube and the X-ray detector are moved in the longitudinal direction of the subject. During the movement, an X-ray is sequentially irradiated to the subject from the X-ray tube. Each time, the transmitted X-ray from the subject is detected by the X-ray detector to capture the X-ray transparent image (top board movement image capturing).
The X-ray image capturing device disclosed in Japanese Unexamined Patent Application Publication No. 2009-254570 can generate an elongate image longer than a single X-ray image by performing joining processing of the X-ray images acquired by the “top board movement image capturing” based on the image capturing position information on the respective X-ray images. Therefore, the X-ray image capturing device of the aforementioned Patent Document 1 is particularly utilized for surgery, etc., which requires a large movement of the image capturing range because it cannot be fit in a single X-ray image as in a lower limb operation.
However, in the X-ray image capturing device as disclosed in Japanese Unexamined Patent Application Publication No. 2009-254570, when moving the image capturing range of the image capturing unit to the position where the operator performs surgery, it is necessary to perform X-ray fluoroscopy to grasp the current image capturing range. Especially, when the movement distance of the image capturing range becomes larger like a lower limb, the time to perform the X-ray fluoroscopy becomes longer correspondingly. Then, in proportion to the time of the X-ray fluoroscopy, the X-ray dose exposing the subject increases. As described above, in the X-ray image capturing device as disclosed in the aforementioned Patent Document 1, in cases where the image capturing range must be moved largely because it cannot be fitted in a single X-ray image, there is a problem that the subject's X-ray exposure dose increases since the X-ray fluoroscopy must be performed during the movement period in which the operator moves the image capturing range to a target position. Incidentally, the “X-ray fluoroscopy” is an image capturing method in which the X-ray dose is relatively reduced as compared with the “X-ray image capturing”, and is temporarily used (not saved).